Traveling wave antenna



Aug. 9, 1949.

N. E. LINDENBLAD TRAVELING WAVE ANTENNA Filed Nov. 11

TfANSM/TTEE TRANS/1W7]??? /N I/ E N 7' 0R- A lLs 1:. L/NDENBLAD A TTORNEV Patented Aug. 9, 1949 TRAVELING WAVE ANTENNA.

Nils E. Lindenblad, Rocky Point, N. Y., assignor to Radio Corporation of America, a corporation of Delaware Application November 11, 1944, Serial No. 562,983

10 Claims.

The present invention relates to traveling wave antennas and, more particularly, to long wire traveling wave antennas.

An object of the present invention is to improve the efficiency of traveling wave antennas.

Another object of the present invention is the provision of a directive antenna which is sub stantially aperiodic over a wide band of frequencies.

Still another object of the present invention is the provision of an aperiodic antenna which is selectively directive in opposite directions.

A further object of the present invention is the provision of a traveling wave antenna which may be simply switched for selective directivity in a pair of opposite directions.

Still a further object of the present invention is the provision of a traveling wave antenna having a low characteristic impedance.

Still a further object of the present invention is the provision of a traveling wave antenna and an unbalanced transmission line system which may be directly connected together without the interposition of reactance circuits.

The foregoing objects are attained by providing a traveling wave antenna in the form of a large diameter cage. The transmission lines associated with the antenna are constructed in the form of large diameter coaxial lines having their outer conductor in the form of a cage similar to the cage forming the antenna. In some cases the antenna itself may form at least a part of the coaxial cage transmission line system for energizing the antenna.

The invention will be more fully understood by referring to the following detailed description which is accompanied by a drawing in which Figure 1 illustrates in simplified diagrammatical form an embodiment of the invention, while ihigure 2 illustrates a modified form of the invenion,

Figure 1 illustrates a two-way traveling wave antenna in which the transmitter is located at a point intermediate the ends of the antenna. The antenna itself is denoted by reference character In. Antenna is in the form of a cage, being constructed of a plurality of wires ll arranged longitudinally on the surface of an imaginary cylinder. The cylindrical formation is maintained by circularly arranged supports. Antenna III has an overall length of preferably at least one wavelength at the operating frequency. It is supported a short distance above ground by suitably arranged poles spaced along the length of the antenna. The supporting structure is not 2 shown in Figure 1, since conventional telephone poles may be used.

As an actual example, the antenna when operating at a frequency of about 1.6 megacycles may have an overall length of about 1200 feet and be supported from 12 to 15 feet above the ground. The antenna may have a diameter of the order of 5 feet. A convenient form of construction utilizes as much as six parallel wires in the cage when the soil resistivity is very low. Thus the characteristic impedance of the antenna may be as low as of the order of 200 ohms. However, When the resistance of the soil over which the antenna is erected is moderately high or higher, a lesser number of wires becomes more efficient. Each end of antenna I0 is arranged to be selectively energized by a transmitter T located intermediate the ends of the antenna. The end of the antenna opposite to the end to which the transmitter is connected is grounded through a terminating resistor R. Resistor R preferably has a resistance equal to the surge impedance of the antenna for which condition energy arriving thereat is absorbed at the rate'of arrival and is hence dissipated without reflection. 'Thus a traveling wave is set up inthe antenna; travelling only from transmitter T to resistor R and having a cumulative radiation effect only in the direction off the end to which resistor R is connected. This cumulative radiation effect originates with the charge displacements taking place in the soil-dielectric-medium. A double-pole, doublethrow switch as indicated by I5 at the transmitter location selects the direction of transmission. The ends of antenna l0 are brought to the transmitter location by transmission lines 20 and 30. Each transmission line includes an inner-conductor 2| surrounded by a cage outer conductor 22. The cage outer conductor 22 is formed of parallel wires 23 arranged about supporting rings 24 in a manner similar to the manner of construction of the antenna Ill. The ratio of cage diameter to the diameter of the inner conductor is so chosen as to give a characteristic impedance equal to the characteristic impedance of antenna l0. Preferably, each of the transmission lines 20 and 30 is grounded at each support, as indicated, by wires 26 running from the support rings 24 to conventional ground symbols. The ground at the antenna input end should be extra good.

Now when switch I5 is thrown, for example, to the right hand position as indicated by reference character E, resistor R is connected to the right hand end of antenna land the transmitter T to the left hand end. Maximum radiation will then be attained off the right hand end of the antenna as indicated by the arrow labeled E. Similarly, if switch is thrown to the left hand position as indicated by reference letter W, resistor R is connected from the left hand end of the antenna [0 to ground and the transmitter T is connected; fromitharight hand end of antenna ID to ground; Maximum radiation is thereby attained off the left hand end of antenna ID as indicated by arrow W.

Under some circumstances it may be desirable to locate the transmitter associated'with 'a traveling wave antenna near onewend'sofuthe -antenna rather than intermediate the ends as *shownin Figure 1. If such is the case, the modification shown in Figure 2 may be used.

In Figure 2, the antenna comprises an outer case structure similar to the cage shownin Figure 1 and in which the corresponding parts of .the' antennalzbear vi corresponding numbers. That is, each of the parallel =wires-iof1the antenna :are' identified byrreferencenumerall l.- and the support; for the? cage: are identified-by reference character. l2.- :fHowever, in'this modificationi'the antenna forms. also a part--oL-the transmission linetrstructure. for selectively energizing the antenna: iorxradiation in a :pair of alternaterdirections. Foruthis pu pose, an inner conductorfliflxpasses through'the entire length of theantenna. 'At one *end conductor it is: di- .rectly and thoroughly-:1: grounded, while at the otherend it passes-into; an extension cage transmission line member iill :whichshould be of relativelysmall length. At the free end of the trans- 'mission'linei 50 the outer conductorcage of the transmission line isuconnected'rto. transmitter T and resistor R.' iilhe'in-ner conductor MB is connected to apair .of :contacts on double-pole, double-throw switch: l5 whilaanother: pair of contacts on' switch" l5 are connected together. and -to'ground. The moving'arms of switch lfirare connected -to the transmitter? and ,resistor R. 'Thus when the switch .is :thrown to the right time position, art E, the transmitter T is directly .connected between the inner conductor lil and rthe outer cageof the transmission 1111953. Also resistor R is connected frorrithe 'end of the outer cage-= to the ground connection. sThus' energy from: transmitter T6 isi.conductedf.-throngh the transmission line' 50 amd'zthrough .the interior. of antenna-l0 actingaas a transmissionli-ne to the remote end of the antenna. There rthe; energy flows back overthe :outer surface of iantenna l Q "and isradiated in the conventional manner. Energy traveling the. entire length i of antenna -I0 and the entire length' of the outer. surf ace' of transmission. line' EG is dissipated "to' ground through resistor R.' Thus maximumradiaticn is :obtained illthe zdirectionof arrow .13. Now if switch. [5 isthrown to thei'eft handmpositiongat 'W;'.the transmitter T iszconnectcd from the outer 2CaSlI1g10f transmission. line Boto the "ground swhiclr :shouldbe adequate for 1311113 purpose while :theeresistorR is1corm'e cted-between the outer casingandconductor 49. With this connection, the energy'from transmitter 'llflows aalong'the outer .:surface of transmission .line 50 along the outer :surface ot'antenna lll. i That which. is .notradiated by thetime itreaches the 'free end ofantenna I0 is conducted back through the interior .of antenna. Ill and along conductor 45!, acting .aslthe innerconductor of a coaxial transmission .line,.-back to .the transmitter location where it is dissipated across resistor R. With this connection the maximum radiation takes place toward the left in the direction indicated by arrow W.

While I have illustrated a particular embodiment of the present invention, it should be clear- 5 1y understood that it is not limited thereto since many modifications may be made in their arrangement and it is therefore contemplated by the appendedT'claims to"=cover"any such' modifications'asfall within the spirit and scope of the invention.

What I claim is:

. 1. A traveling wave antenna including an elongated conductor having an overall length equal to; at :least onewavelength at the operating =frequency, said conductor being constructed in the formof a wire cage, means for selectively electricallyconnecting a source of high frequency energy to either end of said conductor, and means for electrically connecting a terminating resistor to the other end, said source and said terminating resistor being: located adjacent one another.

2; Awtraveling wave antenna including an elongated conductor having 1 an overall length equal to at :1east-one-"Wave1ength at the operating frequency, said conductor being constructed in ;the form of a wire .cage,means for selectively electricallyiconnecting a source'of high frequency energy-toeither end of said conductor, and means for electrically connecting a terminating resistor to the other end, said source' -and 1 said terminating resistor being located adjacent. one another, said connecting means including a coaxial transmissionline having an inner conductor andan outer. conductor in the-form. of a wire cage.

3; A- traveling wave antenna including an elongated conductor having; an overall length equal to. at least 'onewavelength at the operating frequency, said conductor beingconstructed in the form of a wire cage, :lmeansifor selectively electricallyrconnectinga source orhighifrequency :energy to either end of saidconductor, and means .for electrically connecting a terminating resistor tozitheother end; said sonrce'and said terminating resistor bein located adjacent one another, said connecting.meansiincluding a .coaxial' transmissionline having an inner. conductor'and' an outer conductor inith'e: formof a wire cage, the ratio of the. diametersaofesaid innerronductor and saidouter conductor being so chosen that the characteristic impedanceof' said transmission line is equaltozthe impedance of said antenna.

4. A 1 traveling wave antenna including an elongated .sconductor. having an overall length equal to at least one wavelengthgat the operating frequencygsaid conductor being-constructed in .theiormiof a wire cagepmeans for selectively electrically connecting a source of high frequencyxienergy to either end of said conductor, and 'meansiorelectrically connecting a. termi- 00 natingresistor to the other endsaid source and said terminating resistor being located adjacent one another, said connecting means including a coaxial transmission-line having an inner conductor and :an outer conductor in the form of a wire cage the ratio of the diameters of said inner conductor and said outer conductor being so chosen that the characteristic impedance or said transmission line is equal to the impedance of .saidwantennaasaid' antenna cage forming at least a portion of the outer conductor of said transmission line.

5. A selectively bidirectional antemia includinga wire cage conductor having an overall length equal to at least. one wavelength at the 751operatingi-requency, a. transmission; line having an outer conductor in the form of a cage connected to said first-named cage at one end and an inner conductor passing through the length of said transmission line and said antenna cage, said inner conductor being grounded at the far end, a source of high frequency and a terminating resistor connected to an end of the other conductor of said transmission line, a ground connection, and means for selectively connecting said source of high frequency to said inner conductor and the other end of said terminating resistor to the ground connection, or vice versa.

6. A selectively bi-directional antenna including a wire cage conductor having an overall length equal to at least one wavelength at the operating frequency, said wire cage having its transverse dimension so chosen with relation to the height of said antenna above ground as to give a low characteristic impedance, a transmission line having an outer conductor in the form of a cage connected to said first-named cage at one end and an inner conductor passing through the length of said transmission line and said antenna cage, said inner conductor being grounded at the far end, a source of high frequency and a terminating resistor connected to an end of the outer conductor of said transmission line, a ground connection, and means for selectively connecting said source of high frequency to said inner conductor and the other end of said terminating resistor to the ground connection, or vice versa.

7. A selectively bi-directional antenna including a wire cage antenna having an overall length equal to at least one wavelength at the operating frequency, a transmission line having an outer conductor in the form of a cage connected to said first-named cage at one end and an inner conductor passing through the length of said transmission line and said antenna cage, said inner conductor being grounded at the far end, a source of high frequency energy connected between the irmer and outer conductors of said transmission line and a terminating resistor connected between said outer conductor and ground.

8. A selectively bi-directional antenna including a wire cage antenna having an overall length equal to at least one wavelength at the operating frequency, a transmission line having an outer conductor in the form of a cage connected to said first-named cage at one end and an inner conductor passing through the length of said transmission line and said antenna cage, said inner conductor being grounded at the far end,

a terminating resistor connected between the in- 55 ner and outer conductors of said transmission line, and a source of high frequency energy connected between said outer conductor and ground.

9. A selectively bi-directional antenna including a wire cage conductor having an overall length equal to at least one wavelength at the operating frequency, a pair of transmission lines each having an outer conductor in the form of a cage, and an inner conductor, one end of each of said transmission lines being electrically connected to an end of said antenna, the other ends of said transmission lines being closely adjacent, a source of high frequency energy and a terminating resistor, and means for selectively electrically connecting said source to either of said transmission lines and said resistor to the other of said transmission lines.

10. A selectively bi-directional antenna including a wire cage conductor having an overall length equal to at least one wavelength at the operating frequency, a pair of transmission lines each having an outer conductor in the form of a cage and an inner conductor, the ratio of diameters of said outer conductors to said inner conductors being so chosen as to give a characteristic impedance equal to the impedance of said antenna, one end of each of said transmission lines being electrically connected to an end of said antenna, the other ends of said transmission lines being closely adjacent, a source of ,high frequency energy and a terminating resistor, and means for selectively electrically connecting said source to either of said transmission lines and said resistor to the other of said transmission lines.

NILS E. LINDENBLAD.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 801,130 Barclay Oct. 3, 1905 1,452,849 Round Apr. 24, 1923 1,602,085 Rice et al Oct. 5, 1926 1,738,459 Stanley Dec. 3, 1929 1,758,044 Hoyt May 13, 1930 1,824,579 Threlkeld Sept. 22, 1931 2,007,640 Carter July 9, 1935 2,267,889 Aubert Dec. 30, 1941 2,267,945 Peters Dec. 30, 1941 FOREIGN PATENTS Number Country Date 14,045/33 Australia Aug. 23, 1933 OTHER REFERENCES An Ideal Cage Antenna and Counterpoise Ground, by G. W. Gravel, found in Wireless Age, July 1921, pp. 25-26. 

